<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <input type="text" id="i1" value="alex">
    <textarea name="" id="i2" cols="30" rows="10"></textarea>
    <select name="" id="i3">
        <option value="hebei">河北省</option>
        <option value="hunan" >湖南省</option>
        <option value="henan" selected="selected">河南省</option>
    </select>
    <button id="change">change</button>

    <script>
        var ele1 = document.getElementById('i1');
        var ele2 = document.getElementById('i2');
        var ele3 = document.getElementById('i3');
        var change = document.getElementById('change');

        change.onclick = function () {
            ele1.value="yuan";
            ele2.value='alex';
            ele3.value='hunan';

            console.log(ele1.value);
            console.log(ele2.value);
            console.log(ele3.value);
        }
    </script>
</body>
</html>